1. Field of the Invention
The present invention relates to the conveyance, storage and disposal of stormwater runoff, and more particularly concerns chambers which facilitate the infiltration of water into underlying substrate and minimize sediment maintenance requirements.
2. Description of the Prior Art
Culverts, catch basins, and storm sewers are the common practices for collecting and conveying stormwater runoff. In some instances such water is discharged directly into the nearest available water body despite the potentially adverse environmental effects of such action. In some other instances, stormwater management facilities are constructed to help manage the quantity and quality of the stormwater. Wet or dry retention or detention basins/ponds represent the most common structural approach to stormwater management. Although more environmentally sound then direct discharge into an existing water body, such stormwater management approaches preclude other uses of the land. This is of particular importance where land values are high and/or space is limited. The open ponds may also be undesirable in locations near airports because of birds attracted by the pond, or in locations where health, liability or aesthetic considerations make them undesirable. Even the use of xe2x80x9cdryxe2x80x9d detention basins frequently results in the same types of problems associated with wet ponds. Without proper maintenance, dry detention basins frequently transform into wet ponds.
Underground systems have also been developed to help manage stormwater and/or sewage system effluent. Those systems most commonly used include rows of large diameter perforated or unperforated pipe with a relatively small pipe protruding at the upper end of the pipe to retard flow for sediment deposition; infiltration trenches, which are basically excavations filled with stone, which may or may not be fed via drain pipes; and sand filtersxe2x80x94typically large, partitioned concrete xe2x80x9cboxesxe2x80x9d with an initial compartment for sediment deposition and a following compartment with sand and under-drains for stormwater filtration. Although in limited use for approximately 10 years, the use of plastic arch-shaped, open bottom stormwater chambers for stormwater management is a relatively novel approach. Plastic stormwater chambers are highly preferable to other types of underground stormwater management systems for several reasons: they are typically less expensive; they are more maintenance xe2x80x9cfriendlyxe2x80x9d; have a longer effective life; and unlike some other types of underground stormwater management facilities, can be located under paved areas. However, all current underground stormwater management systems are limited by the amount of area available for their installation.
In a typical installation, elongated hollow plastic chambers are emplaced in the ground to form a leaching field for receiving such waters and dispensing them into the surrounding earth. Such chambers have a central cavity for receiving inflow water. An open bottom, and apertures in the sides of the chamber provide the means whereby the water is allowed to exit the central cavity and disperse into the surrounding earth. The chambers are usually attached endwise to form long rows extending in side-by-side juxtaposition in a multi-row array that constitutes a leaching field. The stormwater is generally conducted to the array of rows by a large diameter header manifold pipe that runs orthogonally to the rows closely adjacent one extremity thereof, similar to an underground pipe storage system. Short feeder conduits convey the water from the header pipe to the end wall of the first chamber of each row. The assemblage of chambers is generally engulfed in coarse backfill such as gravel or rock and overlying compacted soil to the surface or to a paved cover surface. The resultant installation may be used as a parking lot, roadway, sports field or for other uses.
The header pipe or manifold system is typically comprised of a 24 inch diameter or larger high density polyethylene (HDPE) pipe with HDPE tees, within which 12 inch lateral pipes are inserted to feed each chamber row. It is not unusual for such a header pipe (manifold) system to be comprised of over 200 feet of HDPE pipe and 50 HDPE tees. A header pipe system of this type becomes very expensive and could easily add over $5,000 to the cost of the stormwater management system and require an additional approximate 2,000 square feet of area for installation.
In order to sustain the considerable downward forces imposed by the surrounding backfill and overhead vehicular traffic, the chambers are generally of arch-shaped configuration having a corrugated construction. The corrugations consist of a continuous sequence of ridges or peaks separated by valleys. The peaks and valleys are connected by web portions disposed in planes substantially orthogonal to the axis of elongation of the chamber.
Examples of such leaching chambers are disclosed in U.S. Pat. Nos. 5,017,041; 5,156,488; 5,336,017; 5,401,116; 5,441,363 and 5,556,231. Such leaching chambers generally have a geometrical configuration which permits nesting, thereby facilitating shipping and storage.
Stormwater may carry considerable amounts of suspended particulate material, commonly referred to as Total Suspended Solids (TSS), which eventually settles out as sediment. The accumulation of such sediment adversely affects the storage capacity of stormwater management facilities, decreasing their effective life. The effective life of such facilities can be extended with a maintenance program for sediment removal.
Unfortunately, the maintenance of stormwater management systems is typically neglected, and occurs when the system fails or sediment accumulates to a point where flooding occurs because of diminished storage capacity of the system. This problem has become so serious that a few municipalities have recently imposed a stormwater maintenance xe2x80x9cfeexe2x80x9d on property owners to help pay for private-sector stormwater facility maintenance. The xe2x80x9cfeexe2x80x9d has not been sufficient in many cases to provide adequate maintenance.
Unlike stormwater wet and dry ponds, which are readily observable and accessible, removal of sediment from underground stormwater management facilities has historically been inherently more inconvenient and costly, resulting in resistance to their use by some municipalities. Some types of underground stormwater management facilities even have to be replaced in order to remove accumulated sediment.
Although leaching fields produced in the aforesaid manner from rows of chambers generally perform in satisfactory manner, their installation is made difficult or impossible when it is required that a header supply pipe with attendant lateral feed pipes (i.e. manifold system) approach the field at one extremity of the rows. Such requirement generally dictates a specialized configuration of excavation required for installing the header supply pipe system in proper relationship to the leaching field and source of the incoming stormwater. A header pipe system could also add significant cost. Not only is extensive excavation required, but extensive amounts of piping may be required for circuitous routings between inlet structures and the header pipe system. The additional land required to access the leaching field may be occupied by buildings or may, for other reasons, be unavailable for excavation. For example, gasoline stations have considerable underground facilities which severely restrict placement of an underground stormwater system. Site limitations of this nature may even preclude the use of underground stormwater systems requiring a header pipe system.
It is accordingly an object of the present invention to provide a stormwater dispensing chamber for producing a leaching field which is more readily accessible to incoming stormwater.
It is another object of this invention to provide a stormwater dispensing chamber as in the foregoing object which facilitates the removal of sediment.
It is a further object of the present invention to provide a stormwater dispensing chamber of the aforesaid nature having sufficient strength to withstand the forces of overlying substrate and inflowing water.
It is yet another object of this invention to provide a stormwater dispensing chamber of the aforesaid nature which provides greater flexibility in accommodating hydrologic and engineering factors in producing a leaching field.
These objects and other objects and advantages of the invention will be apparent from the following description.
The above and other beneficial objects and advantages are accomplished in accordance with the present invention by an improved water dispensing chamber fabricated as a monolithic plastic structure comprising a wall elongated upon a straight axis between inlet and exit ends and having the cross-sectional shape of an arch with upwardly directed peak, said wall defining an open bottom bounded by lowermost spaced apart parallel edges of said wall, said wall further having a multiplicity of alternating peaks and valleys disposed in planes orthogonal to said axis. Interconnecting means located adjacent each end as integral features of said wall allow end-to-end joinder of contiguous chambers to form rows which permit communicating passage of water. In the improved dispensing chamber of this invention, inlet portal means are provided in said arch shaped wall in at least two sites on laterally opposite sides of said axis.
In a preferred embodiment of the improved chamber of the present invention, the exit end of the chamber is provided with flow-impeding means such as an apertured panel extending transversely with respect to said axis between opposite sides of said wall.